Getting value from hidden row column

I have 7 columns in my datatable with 2nd column is invisible and storing Message Id. 3rd column is a checkbox which is visible and i am storing Message Id value there too. Currently when someone checks checkbox i am collecting Message Id value from the checkbox but i don't want to store Message Id value in checkbox instead would like to collect it from the invisible second column.I want to do that in my function event.

function saveCheckedMessages(){
var msgIds = new Array();
$("#tblInbox td input[type=checkbox]:checked").each(function () {
msgIds.push(convertStringToInt($(this).val()));
});
}

How can i achieve that?
here's the link for Datatable
http://debug.datatables.net/ecevic